This invention relates to an infusion catheter for use in supplying fluids such as nourishment, drugs, blood, and colloids simultaneously to different locations in a patient's vein, and more particularly to such an infusion catheter which can be inserted using a guidewire of the Seldinger type.
U.S. patent Ser. No. 4,072,146 which issued on Feb. 7, 1978 to Randolph M. Howes teaches the use of a single catheter providing three distinct lumens for infusion at different locations along the length of a vein containing the catheter. The Howes patent indicates that prior to the application for that patent, venous catheter devices each provided a single lumen which could be used for one purpose only. These purposes included administering drugs or I.V. feeding, monitoring venous pressures or withdrawing blood samples. The disadvantage of this approach is that a catheter must be provided for each one of these functions. Further, the catheter can not be used other than for the single function because it is undesirable and contraindicated to mix many of the drugs and I.V. fluids prior to their entering the blood stream. Also, withdrawal of blood samples can not be performed through a catheter that has previously supplied drugs.
Because it was common in intensive care situations to administer a plurality of drugs simultaneously, there was a need to provide a structure capable of doing this without requiring multiple insertions with the resulting associated trauma. This was particularly true in situations where patients required insertion of catheter devices simultaneously in major veins such as the external or internal jugular, subclavian, cephalic, femoral or saphenous veins. This multiple insertion could result in considerable risk to the patient, discomfort, and possible bleeding and infection. Further, because it is necessary to move the location of the catheters periodically, new punctures must be made with resulting further discomfort and possible complications.
The Howes patent approached the problem by providing a single catheter with multiple lumens which terminated at different locations along the length of the catheter. As a result, when the catheter was inserted in a vein it would provide access to different locations in the vein. The improved venous catheter device was used together with a needle as a venipuncture device, or apart from a needle in which case a vein was exposed and partially transected for direct insertion of the catheter.
To achieve these ends, Howes provided structures of several types. The first was an outer sheath containing individual tubes to define the lumens and they had to be attached to the sheath where infusion was to take place. An alternative was to provide an extrusion having several lumens and which again opened in the side wall of the catheter. In both cases the distal or leading end of the catheter was simply cut from the sheath or the extrusion to provide an opening for one of the lumens.
While the Howes structure has opened the way for an approach using a single catheter with multiple lumens, it has not addressed some of the fundamental problems existing in the art of catheter insertion.
First of all it is evident that a catheter, no matter how many lumens it contains, must have minimal cross-section in order to interfere as little as possible with the flow of blood in the vein, and also to facilitate insertion. Consequently it is necessary to define the cross-section in such a way that the lumens are contained as efficiently as possible in a minimal crosssection while at the same time providing sufficient rigidity and compression resistance that the catheter will have minimal likelihood of kinking or collapsing in use. Further, modern catheter placement commonly dictates the use of the Seldinger technique which is a technique for guiding a catheter over a wire. This minimizes trauma and, with suitable catheter shape, can dilate the body tissue as it is inserted thereby ensuring a good seal and minimal bleeding. Howes structure is not capable of being inserted this way and is in fact designed specifically to be inserted either with an oversized needle, which of course would result in a enlarged opening in the body tissue, or by an incision which would have similar results.
A further consideration when inserting catheters into veins is the rigidity of the tip section. A softer tip is desirable so that it will not tend to apply a load to the wall of the vein while it is in position. Consequently, a reduced diameter at the tip together with some reduction in the hardness of the material is desirable.
In an attempt to improve over the structures shown in U.S. patent Ser. No. 4,072,146, Howes adopted a structure shown in U.S. patent Ser. No. 4,894,057 which issued on Jan. 16, 1990. However this structure, although an improvement over that shown in U.S. Pat. No. 4,072,146, continues to use the same form of insertion as in the prior patent. This may not be readily apparent by reading U.S. Pat. No. 4,894,057 but is is clear when it is related to the earlier patent that the same type of insertion must be used. If the structure shown in U.S. Pat. No. 4,894,057 were to be moved over a guidewire, then the ends of the lumens which terminate short of the tip would cut into body tissue and become occluded. This is clearly dangerous and it is evident that the structure must also be inserted either within a needle or by a cut down technique.
The inherent disadvantages of the Howes structures are detrimental to the use of a multiple lumen catheter for multiple infusion.
It is accordingly an object of the present invention to provide a multiple lumen infusion catheter having a minimal cross-section and which can be inserted using the Seldinger technique to minimize trauma and provide an efficient insertion with minimal bleeding.